Exercise and Protein Supplements

Introduction

Containers of protein powders line the shelves of many supplement stores and are typically a highly purchased product. Protein supplements can be used for a variety of reasons such to help build muscle mass, help with exercise recovery, and can even be used as a meal replacement. Due to the wide variety of usages, this supplement will be used by many types of people and found commonly in a physical therapy clinic. As a physical therapist it is crucial to know how protein metabolizes, the different types of protein supplements that are commonly sold, the effects on timing of ingestion of protein supplements, how protein effects different types of exercise, how age and gender influence protein supplementation, and lastly any additional side effects protein supplements may have.

Types of Protein Supplements

Protein supplementation has a wide variety of options. Here is a general list of the most common types of supplementation available:

Whey

Whey is a protein that is a by-product in cheese production. Whey accounts for 20% of the protein found in milk. This protein metabolizes fast and is the most popular type of the three. Whey is also high in muscle-building amino acids like leucine, isoleucine, and valine. There are two main types of whey protein sold as well as a blend of the two together. These variations are Whey Isolate and Whey Concentrate. Isolate tends to be higher quality and contains between 90 and 98% protein. Concentrate contains between 70 and 85% protein .

Casein

Casein is a protein that makes up the remaining 80% of the protein in milk. Casein digests slowly and is a popular choice as a weight gainer. It contains a little more than 90% protein in general and encourages the body to metabolize carbs and fats first. Casein is also a popular choice for muscle building.

Soy

Soy protein is a fast digesting protein that is of high quality. It is not as efficient as the milk proteins; therefore, it is not as desirable for those looking to build muscle.

Soy protein supplementation has had a lot of controversy over its effect on muscle through use with resistance training, but also the positives and negatives of some of its potential side effects. The main content of soy protein supplements is the soy bean. In a 2006 study, the effects of whey and soy protein with resistance training young men and women in comparison to a blinded control group. The results showed that soy protein in combination with resistance training produces the same effects as whey protein supplementation. 

How Protein Metabolizes and Protein's Effects on the Body

Protein metabolism in the body occurs differently from the other macronutrients, as there is no type of storage for proteins. Proteins are composed of Carbon, Hydrogen, and Oxygen, and Nitrogen. Amino acids are the building blocks of proteins, and are connected by peptide bonds . Amino acids are the usable form that is necessary for digestion to occur. There are 9 essential amino acids that must be consumed, and 11 non-essential amino acids that can be synthesized in the body. A complete protein contains all 9 essential amino acids, while an incomplete protein lacks one or more essential amino acids. Complete proteins are typically seen in animal products, while incomplete proteins are commonly seen in plant sources.

Protein metabolism begins in the stomach. The enzyme pepsinogen in converted to the active pepsin form when in the presence of the highly acidic hydrochloric acid (HCl). Pepsin begins to break down the peptide bonds to form dipeptides and amino acids necessary for digestion. Enzymes, including Trypsin, Chymotrypsin, and Carboxypeptidase, from the pancreas and small intestine are also secreted when needed to break any remaining peptide bonds that escaped the stomach. The amino acids are then absorbed in the small intestine and released in the blood stream .

Proteins are responsible for a number of roles in the body. However, while carbohydrate and fats can be used for energy, proteins do not supply energy directly to the body. Instead proteins are utilized to form blood transporters, enzymes, participate in hormonal regulation, fluid balance, and acid-base balance, and act as a structural component in connective tissue and muscle .

Protein Digestion, Absorption, and Excretion

Timing of Protein Supplementation

"The timing of protein ingestion has been identified as another key factore modulating post-exercise muscle protein anabolism."

Protein ingestion before and/or during exercise:

Minimal research exists supporting the positive impact of protein supplementation before or during exercise. The majority of studies completed have been inconclusive; however, one study showed that the ingestion of protein before and/or during exercise "stimulates muscle protein synthesis during exercise. Therefore, protein ingestion before and/or during prolonged exercise training may inhibit muscle protein breakdown, stimulate muscle protein synthesis, and further augment the skeletal muscle adaptive response to exercise training." The same study stated that, "Dietary protein ingestion before and/or during exercise may provide more effective feeding strategy to improve amino acid availability during early post-exercise recovery."

Protein ingestion after exercise:

The following research statements summarize the effects of post-exercise protein supplementation on related physiologic processes.

"The intake of protein after resistance training increases plasma amino acids, which results in the activation of signaling molecules leading to increased muscle protein synthesis and muscle hypertrophy."

"Dietary protein ingestion after exercise increases post-exercise muscle protein synthesis rates, stimulates net muscle protein accretion, and facilitates the skeletal muscle adaptive response to prolonged exercise training."

"beneficial effects such as reduced muscle soreness and markers of muscle damage become more evident when supplemental protein is consumed after daily training sessions."

In one study researchers investigated the impact of amino acid (lysine, proline, alanine, and arginine) and/or conjugated linoleic acid (CLA) supplements administered before and after aerobic exercise on body weight, percentage body fat, waist and hip circumference, triglycerides and LDL-cholesterol levels . When compared to the placebo group, the waist and hip circumference and BMI of the experimental group after aerobic exercise was a clinically significant.

Types of Exercise and Protein Supplementation

Aerobic Exercise 

Energy and macronutrient needs, especially carbohydrate and protein, must be met during times of high physical activity to maintain body weight, replenish glycogen stores, and provide adequate protein to build and repair tissue.The American Dietetic Association takes the stand that during extreme bouts of exercise, replenishment of CHO and Pro stores are necessary to rebuild tissues in response to the extra protein while extra CHO will restore the glycogen reserve, and both macronutrients will maintain body weight. Endurance athletes usually take CHO supplements during long bouts of exercise to replenish their glycogen stores in order to continue their workout. Studies have been done to prove that carbohydrate-protein (CHO-Pro) supplementation taken after a bout of exercise improves the performance of an endurance athlete and if ingested during a bout of exercise protein oxidation is increased. Even though further research is needed, it is hypothesized that protein use as an energy source is increased during a glycogen-depleted state. Improved recovery and less muscle damage have been associated with CHO-Pro drinks post--exercise. More research is needed to understand the effects of CHO-Pro post-exercise but some studies have revealed improvements in “glycogen repletion, protein balance, muscle-damage, and subsequent performance”(Saunders).  No matter the controversy, CHO-Pro drinks have a lot of potential for endurance athletes during and post-exercise. The balance of protein could be improved, muscle damage could decrease and a positive effect on future performance could occur due to the increase of protein intake in aerobic athletes. 

Additional Side Effects

In addition to its effects on muscles, the use of protein supplements may also come with a number of other side effects, both chronic and acute. Several studies have shown that increased protein intake through the use of protein supplements can have the effect of lowering both systolic and diastolic blood pressure. Its use may therefore be beneficial in managing the blood pressure of those with hypertension. However, one needs to exercise caution with protein supplementation for those whose blood pressure is already low or who are taking medication that lowers blood pressure, as it may increase hypotension-related risks. 

Because protein intake also causes an increase in blood insulin levels, studies have shown that it can significantly lower blood sugar levels. This effect is most pronounced following the ingestion of whey protein, but is still noticeable with the ingestion of protein from other sources. The following graph is from a study comparing blood glucose levels after ingesting a plain glucose drink with blood glucose levels after ingesting the same glucose drink mixed with whey protein: 

Blood glucose levels were clearly much lower when whey protein was ingested. It is therefore important to be mindful of this effect on blood sugar levels when one already has low blood sugar or when one may be taking insulin for diabetes. Failing to do so could potentially increase dangerous hypoglycemia-related risks.